[Mesa-dev] [PATCH] nvc0/ir: propagate immediates to CALL input MOVs

[Tobias Klausmann]

On using builtin functions we have to move the input to registers $0 and $1, if
one of the input value is an immediate, we fail to propagate the immediate:

...
mov u32 $r477 0x00000003 (0)
...
mov u32 $r0 %r473 (0)
mov u32 $r1 $r477 (0)
call abs BUILTIN:0 (0)
mov u32 %r495 $r1 (0)
...

With this patch the immediate is propagated, potentially causing the first MOV
to be superfluous, which we'd remove in that case:

...

mov u32 $r0 %r473 (0)
mov u32 $r1 0x00000003 (0)
call abs BUILTIN:0 (0)
mov u32 %r495 $r1 (0)
...

Shaderdb stats:
total instructions in shared programs : 4893460 -> 4893324 (-0.00%)
total gprs used in shared programs    : 582972 -> 582881 (-0.02%)
total local used in shared programs   : 17960 -> 17960 (0.00%)

                local        gpr       inst      bytes
    helped           0          91         112         112
      hurt           0           0           0           0

Signed-off-by: Tobias Klausmann <tobias.johannes.klausmann at mni.thm.de>
---
 .../nouveau/codegen/nv50_ir_lowering_nvc0.cpp       | 21 +++++++++++++++++++--
 1 file changed, 19 insertions(+), 2 deletions(-)

diff --git a/src/gallium/drivers/nouveau/codegen/nv50_ir_lowering_nvc0.cpp b/src/gallium/drivers/nouveau/codegen/nv50_ir_lowering_nvc0.cpp
index c8f0701572..861d08af24 100644
--- a/src/gallium/drivers/nouveau/codegen/nv50_ir_lowering_nvc0.cpp
+++ b/src/gallium/drivers/nouveau/codegen/nv50_ir_lowering_nvc0.cpp
@@ -47,8 +47,25 @@ NVC0LegalizeSSA::handleDIV(Instruction *i)
    int builtin;
 
    bld.setPosition(i, false);
-   bld.mkMovToReg(0, i->getSrc(0));
-   bld.mkMovToReg(1, i->getSrc(1));
+
+   // Generate movs to the input regs for the call we want to generate
+   for (int s = 0; i->srcExists(s); ++s) {
+      Instruction *ld = i->getSrc(s)->getInsn();
+      ImmediateValue imm;
+      // check if we are moving an immediate, propagate it in that case
+      if (!ld || ld->fixed || (ld->op != OP_LOAD && ld->op != OP_MOV) ||
+            !ld->src(0).getImmediate(imm))
+         bld.mkMovToReg(s, i->getSrc(s));
+      else {
+         bld.mkMovToReg(s, ld->getSrc(0));
+         // Clear the src, to make code elimination possible here before we
+         // delete the instruction i later
+         i->setSrc(s, NULL);
+         if (ld->getDef(0)->refCount() == 0)
+            delete_Instruction(prog, ld);
+      }
+   }
+
    switch (i->dType) {
    case TYPE_U32: builtin = NVC0_BUILTIN_DIV_U32; break;
    case TYPE_S32: builtin = NVC0_BUILTIN_DIV_S32; break;
-- 
2.14.0